Mounting an object that is required to be positioned and fixed in a potentially infinite number of locations on a support in a manner that provides stable and secure attachment while allowing universal positioning of the mounted device has long been a challenge. Over the years the prior art has proposed a number of solutions to this problem, particularly with respect to the positioning of cameras on tripods or other supports. U.S. Pat. No. 318,480 to Kendrick, for example, discloses a joint structure between a camera and tripod that enables the camera to be universally adjusted on the tripod without adjusting the tripod. The joint described in this patent includes a semispherical cup or depression that supports a ball clamped in the cup. Bearing strips located in grooves in the cup provide a secure fit while avoiding expensive turning or finishing work. A thumbscrew holds the ball in the cup once the camera has been moved to a desired position. If it is desired to move the camera to another position, the thumbscrew must be loosened, the camera positioned in the new position, and the thumbscrew retightened. This process must be repeated each time the position of the camera is changed.
A mounting apparatus for a security or surveillance camera is described in U.S. Pat. No. 5,790,910 to Haskin. This mounting apparatus, which includes a ball and socket type of connection between the camera and the support in a swivel assembly, permits adjustment of the horizontal (pan) and vertical (tilt) position of the camera. A locking screw, which secures the camera in the desired position, must be disengaged and reengaged to change the camera's position. The ball does not freely rotate in the socket unless the locking screw is disengaged; however, the locking screw must be engaged to hold the ball in the socket so the camera can maintain the desired position. This arrangement would be likely to be limited to use with relatively light weight cameras.
Symmetrical half shells define a socket in a tripod head in U.S. Pat. No. 5,772,164 to Shen. This socket supports a ball on a camera mounting platform, and a lock screw, hexagon nut and cap nut assembly are required to adjust the spacing between the half shells, so that the ball can be moved to position the camera. This multiple component structure requires unnecessarily complicated maneuvers to move the ball so the camera is fixed in the desired position and then to insure that the camera is held in this position.
U.S. Pat. No. 6,209,830 to Brotz and U.S. Pat. No. 6,439,518 to Brotz et al disclose apparatus for mounting a camera on a tripod platform wherein a pear-shaped ball attached to the camera is inserted into a substantially cylindrical cradle cup attached to a tripod so that the camera can be rapidly mounted on or removed from the tripod. An O ring positioned in a groove in the cradle cup holds the ball in the cup. The static friction between the ball and the cup is stated to be sufficient to hold the camera in any set position, yet the sliding friction is low enough to allow easy movement of the camera to other desired positions. The nonspherical shape of the ball, however, limits the range of positions in which the camera can ultimately be fixed, and the effective frictional forces will be reduced as the components of this apparatus, particularly the O ring, are subject to wear.
A tripod head with a universal joint is described in U.S. Pat. No. 6,352,228 to Buerklin. A metal ball joint mounted in a bearing housing is releasably connectable to an axial element rotatably mounted outside and adjacent to the ball joint housing. The axial element includes a friction element, preferably made of rubber, to connect the axial element to the ball joint. The bearing housing does not conform to the configuration of the ball joint, but supports the ball by ring bearings. A clamping ring in the bearing housing is set or released to fix the ball joint in a desired position. Since the bearing housing does not support the ball in a receptacle having a corresponding radius of curvature, the range of movement of the ball, and thus the camera, is limited by this structure.
A magnetic camera support is described and shown in U.S. Pat. No. 3,286,212 to Thompson. A first part of the magnetic support is secured to a camera and a second part of the magnetic support is secured to a camera tripod. The parts are shaped to be interfitted with one another and are constructed of material with magnetic properties so that when the camera is secured to the tripod relative movement between them does not occur. A plurality of fasteners is required to hold the parts of the magnetic support together. Although this arrangement provides a secure and stable support for the camera, it does not permit universal movement of the camera relative to the support.
Ball and socket types of connectors incorporating magnets and used for diverse purposes are known. U.S. Pat. No. 4,719,549 to Apel, for example, shows a ball and socket connector useful for an illumination system. This connector incorporates a commercially available ball and socket joint including a magnetic holder with a hemispherical recess for receiving a ball made of a magnetic material. Since these magnetic joints must be configured to establish electrical contact, they must be conductive. The arrangement described by Apel would not be useful for positioning and holding in place a heavy object. Moreover, the magnetic ball could not be used with digital cameras or other devices that are magnetically sensitive. Likewise, the magnet-containing ball and socket joint disclosed in U.S. Pat. No. 6,350,076 to Wagner et al, which is part of an apparatus that holds surgical instruments, would not be an effective positioning and support structure for large or heavy positionable objects. The arrangement of the magnetic element relative to the ball and socket in this patent requires an actuation element to produce the axial displacement of arms attached to the ball and socket components of the system described. Such an arrangement may have a useful positioning function; however, it does not suggest how it could concurrently support and universally position a positionable object.
The prior art, therefore, fails to provide a simple magnetic mounting assembly that securely and stably supports and rapidly universally positions a wide range of sizes and weights of positionable objects on supports that employs a combination of magnetic and frictional forces to permit the positionable device to be easily attached to the support so that the positionable object may be easily moved and rapidly variably fixed in a selected one of an infinite range of positions relative to the support without locking devices or actuating mechanisms.